Coating material recovery process



July 6, 193 7.

S. G. SAUNDERS Er AL COATING MATERIAL RECOVERY PROCESS Filed July 14,1936 2 Sheets-Sheet l 3 f QSEYM OUR a. SAUNBEHE AND HARRY MORRlON.

GttornegS y 1937- s. G. SAUNDERS ET AL 2,086,514

COATING MATERIAL: RECOVERY PROCESS Filed July 14, 1936 2 Sheets-Sheet 2lhwemor \SEYM OUR G. 6A UNDERS AND HARRY MORRIQSON.

Gttornegs as to return them to a condition suitable for reprovide animproved method of this character Patented July 6, 1937 COATING MATERIALRECOVERY PROCESS Seymour G. Saunders, Birmingham, and Harry Morrison,Detroit, Mich, assignors to Chrysler Corporation, Highland Park, Mich,a. corporation of Delaware Application July Serial No. 90,559

a precipitating agent of this character in the presence of excessquantities of which the solids or non-volatile constituents of thesurface coating material are insoluble in the solvent of the latter andin which such solvent is either soluble or mixable.

Still further objects of the invention are to provide in the force.draft air passage of a spray booth, curtains of liquid material forwashing out the solid constituents of the air passing from the booth;and to provide curtains of liquid material which serve as precipitatingagent for the particular type of solids of the coating material beingsprayed in the booth.

Another object of the invention is to provide a coating materialrecovery and reconditioning process and apparatus by which the recoveredproducts can be used in compounding materials of the same or differentcharacter from which they were derived or in manufacturing articles ofdiverse compositions.

Additional objects of the invention are to provide an improved exhaustsystem for spray coating booths which is particularly adapted tofacilitate the removal of solid coating material constituents from theair exhausted therefrom; to provide means in the exhaust system of aspray chamber for reversing the course of the flow of the air passingtherefrom and substantially simultaneously subjecting the air to a spraywhile its course of travel is being reversed; to provide an outlet forthe spray liquid and solid material collected thereby which is spacedfrom the normal path of the main portion of the air being exhausted fromthe spray boating chamber; and to provide a sump for collecting thesprayed washing liquids and solid matter collected thereby.

Another object of the invention is to provide a plurality of separatesumps for receiving liquid washing mediums carrying respectivelydifferentlycolored coating material constituents; to provide a pluralityof outlets for the washing medium, each of which is adapted tocommunicate with one of the sumps respectively; and to provideselectively controllable means which are adapted to be so positioned asto direct the differently colored solid coating material constituents totheir respective sumps.

In general, the ingredients of surface coating materials can be broadlyclassified as volatile and non-volatile solvents, non-volatile vehicle,pigment and coloring matter, and driers. In the manufacture of suchcoating materials a large part of the time, labor and machinery cost in-13 Claims.

This invention relates to an improved method and apparatus forrecovering the non-volatile ingredients of sprayed surface coatingmaterials, commonly called solids, from the atmosphere of the space inwhich they are applied, and is a continuation in part of ourapplications, Serial No. 19,794, filed May 4, 1935, and Serial No.45,962, filed October 21, 1935.

More particularly, the invention pertains to the recovery of solids ofpaint, lacquer, natural enamel, synthetic enamels and the like.

The term solids, as used herein and as conventionally employed in thesurface coating art refers to those portions of surface coating materialwhich remain, either in their initial or chemically altered form, in anormally set deposit of such coating materials, including thenon-volatile vehicle and pigment.

One of the main objects of the invention is to by which the recoveredproducts are retained in such condition that they can be readilydissolved in, or dissociated throughout a solvent with which they hadpreviously been associated, so

use in an identical manner.

Another object of the invention is to provide a recovery method of thischaracter by which substantially all the solids of the coating materialof the air withdrawn from the vicinity of the application of coatingmaterials is precipitated and collected.

Another object of the invention is to provide a suitable precipitatingagent for the particular solids of the coating material to be recovered,which both separates the coating material from the air and precipitatesthe solids thereof from their solvent, while leaving the pigment of thecoating material thoroughly dispersed throughout the vehicle thereof,and in condition to be re-incorporated in a solvent without requiringregrinding.

Another object of the invention is to provide precipitating agents ofthis character which lubricate the recovered material or the surfaceswith which the recovered material contacts or which otherwise render therecovered material non-adhesive to such surfaces.

A further object of the invention is to provide an improved method andapparatus for recovering the solids of sprayed coating materials whichprevents oxidation thereof and conversion of the recovered product to aninsoluble, or other state not suited for re-use in coating operations.

Another object of the invention is to provide volves the grinding of thepigment into a finely divided and dispersed state in the non-volatilevehicle. Any recovery process during which this dispersion of pigmentand npn-volatile vehicle is destroyed, naturally falls far short ofsaving these cost factors. In the present process the nonvolatilevehicle is recovered with the pigment dispersed therein substantially asthoroughly as it was in the initial surface coating material. Briefly,this is accomplished by precipitating the solids in the form of a sludgewith the pigment thoroughly dispersed in the vehicle by treating excesssprayed coating material with a liquid, in

the presence of excess quantities of which the solids are insoluble andimmiscible in the solvent.

An illustrative embodiment of the invention is shown in the accompanyingdrawings, in which:

Fig. 1 is an end elevational view of a spraying booth equipped withsolid coating material constituent recovering apparatus embodying theinvention.

Fig. 2 is a horizontal sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is a vertical sectional view taken on the line 3-3 of Fig. 2.

Fig. 4 is a fragmentary sectional view taken on the lined-4 of Fig. 3.

Fig. 5 is a fragmentary illustrative horizontal sectional view taken onthe line 5-5 of Fig. 3 and in addition showing a precipitating agentrecirculating system.

In the drawings is shown one form of spray chamber, generally designatedby the numeral Ill, with which the solid matter recovery apparatus maybe used. The spraying chamber includes a casing having end walls llprovided with registering openings l2 for accommodating the passage ofarticles l3 through the interior thereof. The articles are preferablyconveyed through the spray chamber III by a conveyor which includes arail l4 extending longitudinally of the chamber l0 and located at theupper extremities of the openings l2 thereof. The rail I4 is adapted tomovably support a plurality of carriers l5 which are preferably attachedto a continuous conveyor chain (not shown). The spray chamber III has aroof H5 in which is formed an air inlet opening 11 that communicateswith a conduit i8 leading from an external or internal source of air.Disposed immediately below the air inlet I1 is an invertedfrusto-conical deflector [9 having vanes 20 so constructed and arrangedas to distribute the air current entering the inlet ll throughoutsubstantially all portions of the interior of the chamber l0. Providedat the lower longitudinal extremity of the spray chamber Ill on the sidethereof opposite from the location at which the coating material isdischarged upon the articles by a spray gun 2|, or other suitable means,is an inclined baifie 22 which slopes downwardly and inwardly toward thecentral portion of the floor 23 of the chamber. An air outlet opening 24is provided in the floor 23 adjacent the lower extremity of the bailie22 for permitting the escape of the air admitted through the inlet 21. Agrill 25 is disposed. in the outl t opening 24 for the purpose ofpreventing the passage of articles or spray gun parts or other deviceswhich may accidentally be dropped in the spraying chamber.

The air current is drawn through the inlet opening I! and through theinterior of the spraying chamber H] by a blower 26 located externally ofthe spraying chamber and having a discharge conduit 21 which preferablyleads to the atmosphere. The blower 26 includes an inlet conduit 21'which communicates with an air passage 28 disposed below the sprayingchamber l0 and extending longitudinally thereof. The passage 28 leadsfrom the outlet at of the spraying chamber In and is provided at itsinlet end with curvilinear bafiles 29 and 30 which direct the airpassing through the outlet 28 rightwardly as viewed in Fig. 3 toward theright extremity of the passage 23; The lowermost baflle 29 extendsrightwardly further than the baflle 30 but it terminates in spacedrelation to the right extremity of the passage 28 so as to permit theair current to be reversed in direction of flow by a curvilinear bafile3! located at the upper right extremity of the air passage, as viewed inFig. 3. The air current flows around the right extremity of thelowermost baflle 29 and then continues in a leftward course toward theblower 26. An eliminator 32 is provided adjacent the outlet of the airpassage 28 for removing any liquid such as spray coating material, orthe precipitating agent introduced into the air current in the mannerhereinafter set forth, before the air enters the blower 26 and dischargepipe 21.

The spray chamber l0 and the air passage 28 are provided with means forsubjecting the air current circulated through the system to the actionof an agent for precipitating the solids oi the excess sprayed coatingmaterial which is carried by the air current. The precipitating agent Ipreferably comprises liquid which not only washes or otherwise removesthe sprayed coating material from the air current but which alsoprecipitates the solid constituent thereof from the solvent in whichthey are incorporated.

In the form of the invention illustrated, a discharge pipe 33 having aplurality of relatively small outlet orifices or other spray formingmeans, extends longitudinally of the spray chamber I 0 and is locatedadjacent the back wall 34 thereof as illustrated in Fig. 3. Theorifices, or spray devices of the discharge pipe 33 are so constructedand arranged as to direct the precipitating agent upon the internalsurface of the rear wall 34 and to cause the liquid to flow downwardlythereon substantially in the form of a sheet or curtain. The liquidprecipitating agent is then directed inwardly toward the outlet opening24 by the inclined baflie 22 and ultimately flows through the outletopenings 24 along with the air current. That portion of the excesssprayed coating material which impinges upon the sheet or curtain ofliquid precipitating agent discharged by the pipe 33 is removed from theair current and the solids thereof are precipitated from their solvent.Any portion of the air ladened with spray coating material which is notsubjected to the washing and precipitated action of the agent dischargedby the pipe 33 is thoroughly treated with precipitating agent by a pairof spray devices 35 and 36 located in the left end portion of the airpassage 28. The uppermost spray device 35 includes a plurality of outletorifices or spray nozzles which discharge the precipitating agent in thedirection of travel of the air current. flowing through the section ofthe passage 28 above the baille 29, and the spray device 26 likewiseincludes a plurality of orifices or discharge nozzies which sprayprecipitating agent in a direction opposite to the direction of flow ofthe air current through that portion of the air passage 26 located belowthe baiile 29. In this manner the precipitating agent is applied to theair current of the passage 28 at the location therein where the aircurrent is reversed in the direction of movement.

Provided in the lower wall of the air passage 28 is an outlet 31 foraccommodating the flow of the precipitating agent and solids of thespray coating material therefrom. The outlet 31 communicates with anelongated passageway or conduit 38 having a plurality of longitudinallyadjacent discharge outlets 39, each of which communicates with aseparate sump 40, as illustrated in Fig. 5. In the illustration shownthere are provided three outlet openings 39 and associated sumps 40,each of which is intended to receive precipitating agent ladened with adifferently colored solid coating material constituent. Although onlythree sumps are illustrated in the drawings, there may be provided asmany thereof asarerequired to separate and segregate the,

solids of differently colored coating materials that are applied in thespray chamber l0.

Each outlet 39 of the conduit 38 is provided with a valve member orother adjustable closure,

illustrated in the drawings as a hinged damper 4|. Each closure 4! isprovided with control mechanism, illustrated in Fig. 3, which includes aball crank lever 42 pivotally mounted on the back wall 43 of the airpassage 28 and having a lower arm 44 pivotally connected with theclosure 4| by a link 45. The bell crank lever 42 also includes an upperarm 46 which is operatively connected with a control rod 41 extendingtransversely of the spray booth and having an operating handle 4I'located within convenient reach of the operator and preferably disposedon that side of the spray booth at which the operator stands. Theclosures 4| may be selectively controlled by the operator to correspondwith the particular color of surface coating material being applied inthe spray chamber In so as to deliver substantially all of theprecipitating agent carrying any colored surface coating material to itsproper sump. When it is not desired to separate the differently coloredcoating materials, they may all be collected in one sump and theresulting recovered product may be used in conjunction withpredominating pigments, such as black, or for protective purposes whereappearance is immaterial.

The recovered solids from many sprayed surface coating materials willsink to the bottom of the sump in the form of a sludge when a properprecipitating agent is employed and in this case the solids may beconveniently removed from the sump 40 by the aid of a liquid perviousscreen 48 which is preferably disposed at the bottom of each sump 40.Cables 49 are attached to the screen 48 and preferably extended over apulley 53 so as to enable convenient vertical movement of the screen 48-from the interior of its sump when it is desired to displace theprecipitated solids therefrom.

With the use of certain precipitating agents for removing the solids ofsome sprayed surface coating materials, it is found that the solidsfloat on the top of the liquid, in the form of a scum or sludge, in thesump 40 and may be conveniently removed therefrom by scraping thefloating scum-like substance so formed into a trough from which it maybe conveniently removed for further operation in accordance with therecovery process.

The precipitated solids obtained in either of the foregoing ways includethe non-volatile vehicle dispersed coloring matter or pigment andsubstantially all other ingredients which comprise the solids of surfacecoating materials. In this recovery product, the pigment is thoroughlydispersed in the non-volatile vehicle in substantially that conditionproduced by the original grinding operations employed' in the initialmanufacture of the coating material. These recovered products are thenseparated from the precipitating agent, preferably by initially removingthe main portion of the latter in a press and then allowing the materialto dry. For some purposes more complete removal of the precipitatingagent is desirable and in this event the precipitating agent ispreferably washed out or extracted, as hereinafter more clearly setforth, with a suitable solvent therefor which will not dissolve orotherwise seriously disturb the condition of the recovered solids. Thethus reconditioned recovered material may then be dissolved in a solventof the same character as that from which it had previously beenseparated in order to produce surface coating material which isotherwise wasted.

Various precipitating agents may be used in the foregoing processdepending mainly upon the particular nature of the coating material fromwhich the solids are to be recovered. In recovering the solids fromcellulose lacquers it is preferable to use water as a precipitatingagent, while in recovering the solids from paint and enamels of thesynthetic and natural type, the use of a mineral oil as theprecipitating agent is particularly advantageous. While a vast number ofmineral oils of different distillation temperatures may be employed forthis purpose, it is preferable to use those which do not readilyevaporate such as mineral oils having a distillation temperature notlower than that of kerosene. Paraifin oil and mineral oils havingdistillation temperatures be- I tween those of paraffin oil, andkerosene operate successfully in recovering solids from sprayed paint,lacquer and enamels as well as from glyptol resin base synthetic coatingmaterials.

The solids of substantially all spraying types of coating materials .canbe economically and commercially recovered by using in the foregoingprocess a precipitating agent comprising an emulsion of soluble oil inwater. This precipitating liquid is particularly suitable for therecovery of natural resin and oil base coating materials and syntheticresin base coating materials such as alkyd, resin base varnishes,enamels and lacquers, and the like. It may be used in the recovery ofnitrocellulose lacquers, but, for the purpose of economy, water isrecommended for recovering this type of coating material. The oilcontent effectively prevents the deposited precipitate from adhering tothe surfaces of the enclosure in which the process is conducted andthrough which such materials are conveyed.

Water miscible oils, commonly called soluble oils, of variouscharactersmay be used in our improved recovery process. These oils are readilymiscible with water and maintain a stable emulsion. When a soluble oilbase derived by treatment of mineral oil, for example, with naphthenicacid is used, it is preferable to neutralize the free acid content witha suitable alkali such as potassium hydroxide or sodium hydroxide. Anysoluble oil base employed should be either neutral or only slightly acidfor the presence of a comparatively strong alkaline condition results insaponification, and hence waste of the resin content of the solids.Other alkali may be used, but the introduction with the alkali ofsolvents for the resins of the solids should be carefully guardedagainst.

Although proportions of soluble 011 base and large excess of washingsolvent.

water of the precipitating medium may vary within wide limits, forpurposes of economy, flowability and general convenience of operation,emulsions of water and oil, respectively, varying from parts of water to1 part of soluble oil base; to 30 parts of water to one part of solubleoil base are preferred.

Irrespectiveof the saving resulting from the recovery of excess sprayedcoating materials, the use of precipitating agents in the foregoingmanner and in which the solids of the coating materialare not soluble orrendered gummy, is of substantial value. The elimination of the nuisanceproblems involved in the discharging of air fromspray booths into theatmosphere in densely inhabited regions, as well as the saving incleaning of the apparatus and removing therefrom, deposited solid andsemi-solid accumulations represent a material saving in spray boothoperation even though no attempt is made to reuse the recovered coatingmaterials.

The precipitating medium may be withdrawn periodically from the sump 40through conduits 52, each having a valve 53 therein, and discharged intoa receptacle 54. The receptacle 54 is preferably provided with afiltering partition 55 through which the liquid precipitating agent mustpass before being returned to the pipe 33 and spray devices 35 and 36through an outlet pipe 56 having a branch pipe 51 communicating with thedischarge pipe 33, and a branch pipe 58 communicating with the spraydevices 35 and 35. The branch pipes 51 and 58 are preferably providedwith valves 59 and 60, respectively, for individually controlling theflow of precipitating liquids to the pipe 33 and spray devices 35 and36, respectively. The precipitating liquid may be recirculated in theforegoing manner and repeatedly redischarged in the spraying cham-' herIt) under the pressure of a pump 6| included in the outlet conduit 56 orotherwise suitably located.

Complete removal of any precipitating agent which remains in therecovered product can be accomplished by washing the material with asuitable solvent for the particular precipitating agent used in therecovery process and in which the solids are insoluble. When mineral oilis employed, solvents such as naphtha, gasoline and other hydrocarbonsolvents, which have distillation temperatures in the neighborhoodthereof, will efliciently and substantially completely remove theprecipitating agent from recovered solids of synthetic resin basecoating materials of the class which include alkyd, phenol formaldehyde,urea formaldehyde, Vinylite and resin base surface coating substances.

The washing operation is preferably conducted in a tank and in thepresence of a substantially It is found that the recovered mass which,in many cases, is of a liver-like consistency, is readily broken up intorelatively small particles by the application of heat (substantially 140F.) and mechanical agitation during the washing operation, thetemperature maintained during the washing may be varied throughoutsubstantial limits depending upon the nature of the composition of thesurface coating material being recovered. The resulting finely dividedparticles of the recovered solid constituent are allowed to settle outand they are thereafter separated from the liquid of the mixture bydrawing off the latter or by filtration, if desired. The reconditionedrecovered material may then be dissolved in toluol,

xylol or any other suitable solvent and prepared for reuse in aconventional manner. When kerosene or a heavy naphtha is employed as aprecipitating agent and thereafter removed from the recovered mass bywashing the latter with light naphtha, the resulting recovered materialcan be readily dissolved in xylol or toluol.

When emulsions of soluble oil and water are used as precipitatingagents, the precipitate is preferably freed from both water and solubleoil base by washing it with an alcohol, preferably denatured alcohol.Any of the alcohols may be used in which the recovered material is notexcessively soluble.

When recovered surface coating materials are treated with alcohol inthis manner and then dissolved in a solvent to condition it for reuse,it is sometimes found that a layer of a solution of alcohol and water ispresent floating on the top of the reconditioned coating material. Thisforeign layer can be conveniently removed by centrifuging the mixture ina separator of the type commonly used as milk and cream separators.

In the production of recovered coating materials for many purposes,sludge recovered by precipitation with water and soluble oil may beseparated from the main bulk of the precipitating medium and directlydissolved in a suitable coating material solvent and the coatingmaterial may then be centrifuged in a separator to remove any remainingsoluble oil and water, thus avoiding the alcohol treatment.

It is found that the oil length properties and metallic dryer content ofsurface coating materials which have been washed with an alcohol aredisturbed somewhat by the alcohol wash. This action of the alcohol canreadily be compensated for by the addition of metallic dryer andrelatively small quantities, say from one to two per cent, of the freefatty acids originally in the resin base of the coating material. Fattyacids may be added in their free state or in the form of fatty acidcontaining drying oil such as linseed oil, soya bean oil and perillaoil. Other drying oils may also be used for this purpose but it ispreferable to use bodied-blown drying oils.

Although but several specific embodiments of the invention are hereinshown and described, it will be understood that various changes in thesize, shape and arrangement of parts may be made without departing fromthe spirit of our invention.

What we claim is:

1. The process of recovering the solids of excess sprayed coatingmaterial which comprises precipitating said solids by subjecting saidexcess sprayed coating material to treatment with a water and oilemulsion including mineral oil emulsifiable in water, and separating theresulting precipitate from said emulsion.

2. The process of recovering solids from airborne particles of sprayedcoating material including a volatile solvent and non-volatile vehiclehaving pigment dispersed therein, which comprises precipitating saidsolids from said solvent and from the air in the form of a sludge havingthe pigment dispersed in the non-volatile vehicle by treating suchair-borne particles with a precipitating agent comprising a water andoil emulsion including mineral oil emulsifiable in water, and separatingsaid precipitating agent from said sludge.

3. The process of recovering the solids of excess sprayed coatingmaterial which comprises precipitating said solids by subjecting saidexcess sprayed coating material to treatment with an alkali free butsubstantially neutral water and oil emulsion including mineral oilemulsiflable in water, and separating the resulting precipitate fromsaid emulsion.

4. The process of recovering the solids of excess sprayed coatingmaterial which comprises precipitating said solids from their solvent bysubjecting said excess sprayed coating material to treatment with awater and oil emulsion including mineral oil emulsiflable in water,removing said precipitate from said emulsion, washing the removedprecipitate with an excess quantity of an alcohol in which said oil issoluble and in which said precipitate is insoluble, and separating thewashed precipitate from the alcohol wash.

5. The process of recovering the solids of excess sprayed coatingmaterial which comprises precipitating said solids by subjecting saidexcess sprayed coating material to treatment with a water and oilemulsion including mineral oil emulsiflable in water, separating saidprecipitate from said emulsion, and incorporating said separatedprecipitate in a coating material solvent.

6. The process of recovering and reconditioning the solids of excessresin base sprayed coating material which comprises precipitating saidsolids from their solvent by subjecting said excess sprayed coatingmaterial to treatment with a water and oil emulsion mineral oilemulsiflable in water, mechanically separating said precipitate fromsaid emulsion, washing said separated precipitate with an alcohol inwhich said oil is solu ble and in which said precipitate issubstantially insoluble, compensating for alcohol disturbed oil lengthproperties of said precipitate by adding thereto relatively smallquantities of a drying oil fatty acid, and incorporating the resultingproduct in a surface coating material solvent.

7. The process of recovering and reconditioning the solids of excessresin base sprayed coating material which comprises precipitating saidsolids by subjecting said excess sprayed coating material to treatmentwith a water and oil emulsion including mineral oil emulsiflable inwater, mechanically separating said precipitate from said emulsion,washing said separated precipitate with an alcohol in which said oil issoluble and in which said precipitate is substantially insoluble,compensating for alcohol disturbed oil length properties of saidprecipitate by adding thereto relatively small quantities of a bodiedblown drying oil, and incorporating the resulting product in a surfacecoating material solvent.

8. The process of recovering and reconditioning the solids of excessresin base sprayed coating material which comprises precipitating saidsolids by subjecting said excess sprayed coating material to treatmentwith a water and oil emulsion including mineral oil emulsiflable inwater, mechanically separating said precipitate from said emulsion,washing said separated precipitate with an alcohol in which said oil issoluble and in which said precipitate is substantially insoluble,compensating for alcohol disturbed oil length properties and alcoholsoluble metallic dryer loss by adding to said precipitate a drying oilfatty acid and metallic dryer, and incorporating the resulting productin a surface coating material solvent.

9. The process of recovering the solids of excess sprayed coatingmaterial which comprises precipitating said solids by subjecting saidexcess sprayed coating material to treatment with a water and oilemulsion including mineral oil emulsiflable in water, removing saidprecipitate from the main bulk of said emulsion, dissolving said removedprecipitate in a coating material solvent, and centrifuging theresulting solution to separate the latter from remaining quantities ofsaid emulsion.

10. The process of recovering solid constituents of excess sprayedcoating material having a vola tile portion including a volatile solventand having a solid content including a non-volatile vehicle and pigmentdispersed therein which comprises precipitating in an enclosure thenonvolatile vehicle and pigment as a sludge with the pigment dispersedtherein whereby said sludge is rendered substantially non-adhesive tothe surface of the container in which it is maintained by treating airborne particles of such coating material with a precipitating mediumcomprising a liquid in the presence of which conversion of the recoveredproduct to an insolube or other state not suitable for re-use issubstantially prevented and particles of said solid content areprecipitated and united together in substantially liver-like massformation, collecting said precipitating medium and said sludge, saidsludge accumulating therein in a mass of liver-like consistencyincluding substantially all the non-volatile ingredients of said excesssprayed coating material in re-usable proportions, and separating saidsludge from said precipitating medium and the unvolatilized portion ofsaid solvent remaining in said medium, whereby said sludge isconditioned to be directly redissolved and re-used as a surface coatingmaterial in a solvent of the same character as that from which it wasprecipitated, and redissolving said solid constituent of said sludge involatile solvent.

11. The process of recovering solid constituents of excess sprayedcoating material having a volatile portion including a volatile solventand having a solid content including a non-volatile vehicle and pigmentdispersed therein which comprises precipitating in an enclosure thenonvolatile vehicle and pigment as a sludge with the pigment dispersedtherein whereby said sludge is rendered substantially non-adhesive tothe surface of the container in which it is maintained by treating airborne particles of such coating material with a precipitating mediumcomprising a liquid in the presence of which conversion of the recoveredproduct to an insoluble or other state not suitable for reuse issubstantially prevented and particles of said solid content areprecipitated and united together in substantially liverlike massformation, collecting said precipitating medium and said sludge, saidsludge accumulating therein in a mass of liver-like consistencyincluding substantially all the non-volatile ingredients of said excesssprayed coating material in re-usable proportions, separating saidsludge from said precipitating medium and the unvolatilized portion ofsaid solvent remaining in said medium, whereby said sludge isconditioned to be directly redissolved and re-usecl as a surface coatingmaterial in a solvent of the same character as that from which it wasprecipitated, redissolving said solid constituent of said sludge involatile solvent, and repeatedly recirculating said precipitating mediumfor re-use.

12. The process of recovering solid constituents of excess sprayedcoating material having a volatile portion including a volatile solventand having a solid content including a non-volatile vehicle and pigmentdispersed therein which comprises precipitating in an enclosure thenon-volatile vehicle and pigment as a sludge with the pigment dispersedtherein whereby said sludge is rendered substantially non-adhesive tothe surface of the container in which it is maintained by treating airborne particles of such coating material with a precipitating mediumcomprising a. liquid in the presence of which conversion of therecovered product to an insoluble or other statenot suitable for re-useis substantially prevented and particles of said. solid content areprecipitated and united together in substantially liver-like massformation, collecting said precipitating medium and said sludge, saidsludge accumulating therein in a mass of liver-like consistencyincluding substantially all the non-volatile ingredients of said excesssprayed coating material in re-us'able proportions, removing said sludgefrom the main bulk of said precipitating medium, whereby said sludge isconditioned to be directly redissolved for re-use as a surface coatingmaterial, dissolving said removed sludge in a coating material solvent,and centrifuging the resulting solution to separate from the latterremaining quantities of said emulsion.

13. The process of recovering solid constituents of excess sprayedcoating material composed of a solution of said solid constituents and asolvent, which comprises separating from the solvent of suchcoatingmaterial substantially all the remaining ingredients thereof as acoherent mass of the particles of said solid constituents byprecipitating said remaining ingredients in an enclosure as a sludgewhereby said solid constituents are rendered substantially non-adhesiveto the surfaces in which they are maintained by treating air borneparticles of such coating material with a liquid in the presence ofwhich said solid constituents are insoluble in their solvent and coheretogether in surface scum-like formation, collecting said solidconstituents in a single layer on said precipitating medium as a surfacescum-like substance, said scum-like substance including substantiallyall the non-volatile ingredients of said excess sprayed coating materialin re-usable proportions,- separating said scum-like substance from saidprecipitating medium whereby said solid constituents thereof areconditioned to be directly redissolved and re-used as a surface coatingmaterial in a solvent of the same character as that from which it wasprecipitated, and forming from said recovered solid constituents acoating material of the same character as that from which they wererecovered by dissolving said solid constituents of said scum in saidcoating material solvent.

SEYMOUR G. SAUNDERS. HARRY MORRISON.

